During the last visit of President Remengesau of Palau to Japan in December 2014, he repeated that Japan and Palau has more than 20 years of diplomatic history, which started before the WWII.
However, according to Tadao Yanaihara who published "Nanyo Gunto no Kenkyu" "Study of South Sea islands" (1935), in 1890 the trade ship Tenyu-maru visited Palau and started trade. So, this year, 2015, is the 125th anniversary of Japan-Palau.
Japan was forced to open its port and agree to an unequal treaty by the US pro-whaler Commodore Matthew Calbraith Perry in the mid 19th century. As a result this, the old government became corrupted and more than one million Samurai lost their job.
One of the sons of the Samurai, Ukichi Taguchi, obtained a compensation grant for Samurai and arranged for the trading ship "Tenyu-Maru" to explore Micronesia in 1890.
Although his challenge failed within in a year and he received criticism, there were a few trading companies established in Micronesia, including Palau.
Even after Germany colonized Palau, Japanese trading companies led most of commercial activities in Palau.
Why did Japan rule the former German colonies of Micronesia after World War I?
This was a result of Japan’s protection of the Pacific, (Australia, New Zealand and the Pacific Islands) with the request from her ally Britian. Japan not only protected the Pacific during WWI, but also all over the world where Britain was hard fighting.
At the beginning Japan was not so keen to obtain the Micronesia islands due to its past bitter experiences. Previously the western power interfered in Japan’s taking over her colonies as the result of the victories of the Japan-Sino War and the Japan- Russia War. In particular Yap isand, which had a communication cable that connected German-US mainland to Asia.
However, as a result of a series of rude, arrogant and unfair actions by both the Australian government and the Royal Australian Navy, Japan developed the conviction to have Micronesia as its colonies. Australia’s attitude is not surprising at that time. They had the notorious “White Australian policy” as a national policy, as well as the well known racial attitude of their Prime Minister, Billy Hughes’, during the Paris Peace Conference.